This invention relates to a flying head slider and a magnetic disk device using the same, and more particularly to a negative pressure flying head slider suitable for a magnetic disk device of a high recording density, and also to a magnetic disk device using the same.
Recently, there has been a demand for magnetic disk devices capable of achieving a higher recording density than before. In a magnetic disk device, there is used a flying head slider which flies while keeping a microscopic distance in relation to a rotating magnetic disk. The flying height can be kept constant at any position over the magnetic disk, and therefore negative pressure flying head sliders, proposed for example in U.S. Pat. No. 5,430,591 and Japanese Patent Unexamined Publication No. 7-169221, have been extensively used.
To attain a high recording density, it is sufficient to make the flying height small. Therefore, the inventors of the present invention have used negative pressure flying head sliders, such as those proposed in U.S. Pat. No. 5,430,591 and Japanese Patent Unexamined Publication No. 7-169221, with a flying height of several tens of nm, and as a result the following problems have been encountered.
In the negative pressure flying head slider such as that proposed in U.S. Pat. No. 5,430,591, it is possible to make the flying height small, but air stagnation appears at that portion (where side rails are not provided) of the slider to the rear of the side rails, so that a lubricant is accumulated on this portion. In a contact.start.stop (CSS) type in which the flying head slider is brought into sliding contact with the magnetic disk when the device is activated (started) and stopped, the lubricant is coated uniformly thin over the entire surface of the magnetic disk in order to enhance the sliding properties. The lubricant has a high viscosity at first, but in accordance with the rotation of the magnetic disk, the lubricant is lowered in viscosity, and floats in a mist-like manner over the magnetic disk. This has not generated any problem when the flying height is as large as 200 nm as in the conventional construction. However, in the case where the flying height is several tens of nm in order to achieve a high recording density, the slider flies at a region where the mist of the lubricant is thick, and therefore it is thought that the lubricant is accumulated on that portion of the slider where the air is stagnant. When the slider, having the lubricant accumulated thereon, is left on the magnetic disk upon stop of the device, the lubricant intrudes between the slider and the magnetic disk, and forms a meniscus, thereby producing a large adhesion force. This adhesion force increases the force to firmly hold the slider on the magnetic disk, and therefore there is a possibility that the magnetic disk device cannot be activated again, and in the worst case a suspension supporting the slider is plastically deformed, thus making it difficult to obtain the optimum flying height, so that a trouble such as a clash of the slider may occur.
On the other hand, in the negative pressure flying head slider such as that disclosed in Japanese Patent Unexamined Publication No. 7-169221, there is no portion to the rear of the side rails where side rails are not provided, and therefore a lubricant will not accumulate on any portion of the slider. However, when the direction of flow of the air into an air bearing surface of the slider becomes out of agreement with the longitudinal axis of the slider (in other words, a yaw angle is formed) due to a seeking operation of the slider, the air obliquely traverses the rails, and therefore a sufficient pressure, produced by the compression of the air, is not obtained at the rail portions, so that the flying height is reduced. Particularly during the seeking operation, the angle at which the air obliquely traverses the rails, increases, so that the flying height is remarkably reduced. The reduction of the flying height upon formation of the yaw angle and during the seeking operation has not caused any problem when the flying height is as large as 200 nm as is conventional. However, in the case where the flying height is several tens of nm in order to achieve a high recording density, there is a possibility that the slider crashes with the magnetic disk upon formation of the yaw angle and during the seeking operation.